title: Rapid antifungal susceptibility testing by matrix-assisted laser desorption ionization-time of flight mass spectrometry analysis.
abstract: The widespread use of antifungal agents, which is likely to expand with their enhanced availability, has promoted the emergence of drug-resistant strains. Antifungal susceptibility testing (AFST) is now an essential procedure for guiding appropriate antifungal therapy. Recently, we developed a matrix-assisted laser desorption ionization-time of flight mass spectrometry (MALDI-TOF MS)-based method that enables the detection of fungal isolates with reduced echinocandin susceptibility, relying on the proteome changes that are detectable after a 15-h exposure of fungal cells to serial drug concentrations. Here, we describe a simplified version of this approach that facilitates discrimination of the susceptible and resistant isolates of Candida albicans after a 3-h incubation in the presence of "breakpoint" level drug concentrations of the echinocandin caspofungin (CSF). Spectra at concentrations of 0 (null), 0.03 (intermediate), and 32 (maximal) μg/ml of CSF were used to create individual composite correlation index (CCI) matrices for 65 C. albicans isolates, including 13 fks1 mutants. Isolates are then classified as susceptible or resistant to CSF if the CCI values of spectra at 0.03 and 32 μg/ml are higher or lower, respectively, than the CCI values of spectra at 0.03 and 0 μg/ml. In this way, the drug resistance of C. albicans isolates to echinocandin antifungals can be quickly assessed. Furthermore, the isolate categorizations determined using MALDI-TOF MS-based AFST (ms-AFST) were consistent with the wild-type and mutant FKS1 genotypes and the AFST reference methodology. The ms-AFST approach may provide a rapid and reliable means of detecting emerging antifungal resistance and accelerating the initiation of appropriate antifungal treatment.
authors.affiliation: Institute of Microbiology, Università Cattolica del Sacro Cuore, Rome, Italy.
authors.forename: Antonietta
authors.initials: A
authors.lastname: Vella
authors.forename: Elena
authors.initials: E
authors.lastname: De Carolis
authors.forename: Luisa
authors.initials: L
authors.lastname: Vaccaro
authors.forename: Patrizia
authors.initials: P
authors.lastname: Posteraro
authors.forename: David S
authors.initials: DS
authors.lastname: Perlin
authors.forename: Markus
authors.initials: M
authors.lastname: Kostrzewa
authors.forename: Brunella
authors.initials: B
authors.lastname: Posteraro
authors.forename: Maurizio
authors.initials: M
authors.lastname: Sanguinetti
mesh_terms: D000935:Antifungal Agents / Q000494:pharmacology*; D002176:Candida albicans / Q000737:chemistry* / Q000187:drug effects; D000077336:Caspofungin; D054714:Echinocandins / Q000494:pharmacology*; D005656:Fungal Proteins / Q000032:analysis; D006801:Humans; D055666:Lipopeptides; D008826:Microbial Sensitivity Tests / Q000379:methods; D020543:Proteome / Q000032:analysis*; D019032:Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization / Q000379:methods*; D013997:Time Factors
chemical_list: D000935:Antifungal Agents; D054714:Echinocandins; D005656:Fungal Proteins; D055666:Lipopeptides; D020543:Proteome; D000077336:Caspofungin